Your helicopter is really amazing! The controling system can almost reach the complexity of vanilla train controling system. Can you extends your framework to ships like those in https://mods.factorio.com/mod/ships_extended? These vehicles works pretty simlar: drive directly, travel from one site to another.
Pathfinding for ships might be tricky as they can only sail in the water, and may strike the land when sailing directly. But we may leave these problems to the user so a trival path finding will only sail directly from harbor A to harbor B, which defined by some landing filed-like building like harbor/lighthouse.
For additional ideas, a multi-stop path finding will better increase the power for both your aircrafts and ships, which may works like: start flying at spot A, pass spot B,C.. and stop at spot E, so they can take complex routes and avoid obstacles for ships. If we can combine conditional automated start/stop on them, like wait at station/harbor A for 30s, or leave when cargo is empty, we can create a fully functional 3D transportation including land, sea and air ;)
